1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * <linux/swait.h> (simple wait queues ) implementation:
4 */
5
__init_swait_queue_head(struct swait_queue_head * q,const char * name,struct lock_class_key * key)6 void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
7 struct lock_class_key *key)
8 {
9 raw_spin_lock_init(&q->lock);
10 lockdep_set_class_and_name(&q->lock, key, name);
11 INIT_LIST_HEAD(&q->task_list);
12 }
13 EXPORT_SYMBOL(__init_swait_queue_head);
14
15 /*
16 * The thing about the wake_up_state() return value; I think we can ignore it.
17 *
18 * If for some reason it would return 0, that means the previously waiting
19 * task is already running, so it will observe condition true (or has already).
20 */
swake_up_locked(struct swait_queue_head * q)21 void swake_up_locked(struct swait_queue_head *q)
22 {
23 struct swait_queue *curr;
24
25 if (list_empty(&q->task_list))
26 return;
27
28 curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
29 wake_up_process(curr->task);
30 list_del_init(&curr->task_list);
31 }
32 EXPORT_SYMBOL(swake_up_locked);
33
34 /*
35 * Wake up all waiters. This is an interface which is solely exposed for
36 * completions and not for general usage.
37 *
38 * It is intentionally different from swake_up_all() to allow usage from
39 * hard interrupt context and interrupt disabled regions.
40 */
swake_up_all_locked(struct swait_queue_head * q)41 void swake_up_all_locked(struct swait_queue_head *q)
42 {
43 while (!list_empty(&q->task_list))
44 swake_up_locked(q);
45 }
46
swake_up_one(struct swait_queue_head * q)47 void swake_up_one(struct swait_queue_head *q)
48 {
49 unsigned long flags;
50
51 raw_spin_lock_irqsave(&q->lock, flags);
52 swake_up_locked(q);
53 raw_spin_unlock_irqrestore(&q->lock, flags);
54 }
55 EXPORT_SYMBOL(swake_up_one);
56
57 /*
58 * Does not allow usage from IRQ disabled, since we must be able to
59 * release IRQs to guarantee bounded hold time.
60 */
swake_up_all(struct swait_queue_head * q)61 void swake_up_all(struct swait_queue_head *q)
62 {
63 struct swait_queue *curr;
64 LIST_HEAD(tmp);
65
66 raw_spin_lock_irq(&q->lock);
67 list_splice_init(&q->task_list, &tmp);
68 while (!list_empty(&tmp)) {
69 curr = list_first_entry(&tmp, typeof(*curr), task_list);
70
71 wake_up_state(curr->task, TASK_NORMAL);
72 list_del_init(&curr->task_list);
73
74 if (list_empty(&tmp))
75 break;
76
77 raw_spin_unlock_irq(&q->lock);
78 raw_spin_lock_irq(&q->lock);
79 }
80 raw_spin_unlock_irq(&q->lock);
81 }
82 EXPORT_SYMBOL(swake_up_all);
83
__prepare_to_swait(struct swait_queue_head * q,struct swait_queue * wait)84 void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
85 {
86 wait->task = current;
87 if (list_empty(&wait->task_list))
88 list_add_tail(&wait->task_list, &q->task_list);
89 }
90
prepare_to_swait_exclusive(struct swait_queue_head * q,struct swait_queue * wait,int state)91 void prepare_to_swait_exclusive(struct swait_queue_head *q, struct swait_queue *wait, int state)
92 {
93 unsigned long flags;
94
95 raw_spin_lock_irqsave(&q->lock, flags);
96 __prepare_to_swait(q, wait);
97 set_current_state(state);
98 raw_spin_unlock_irqrestore(&q->lock, flags);
99 }
100 EXPORT_SYMBOL(prepare_to_swait_exclusive);
101
prepare_to_swait_event(struct swait_queue_head * q,struct swait_queue * wait,int state)102 long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
103 {
104 unsigned long flags;
105 long ret = 0;
106
107 raw_spin_lock_irqsave(&q->lock, flags);
108 if (signal_pending_state(state, current)) {
109 /*
110 * See prepare_to_wait_event(). TL;DR, subsequent swake_up_one()
111 * must not see us.
112 */
113 list_del_init(&wait->task_list);
114 ret = -ERESTARTSYS;
115 } else {
116 __prepare_to_swait(q, wait);
117 set_current_state(state);
118 }
119 raw_spin_unlock_irqrestore(&q->lock, flags);
120
121 return ret;
122 }
123 EXPORT_SYMBOL(prepare_to_swait_event);
124
__finish_swait(struct swait_queue_head * q,struct swait_queue * wait)125 void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
126 {
127 __set_current_state(TASK_RUNNING);
128 if (!list_empty(&wait->task_list))
129 list_del_init(&wait->task_list);
130 }
131
finish_swait(struct swait_queue_head * q,struct swait_queue * wait)132 void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
133 {
134 unsigned long flags;
135
136 __set_current_state(TASK_RUNNING);
137
138 if (!list_empty_careful(&wait->task_list)) {
139 raw_spin_lock_irqsave(&q->lock, flags);
140 list_del_init(&wait->task_list);
141 raw_spin_unlock_irqrestore(&q->lock, flags);
142 }
143 }
144 EXPORT_SYMBOL(finish_swait);
145